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cgroups: fix lock inconsistency in cgroup_clone() 

I fixed a bug in cgroup_clone() in Linus' tree in commit 7b574b7
("cgroups: fix a race between cgroup_clone and umount") without noticing
there was a cleanup patch in -mm tree that should be rebased (now commit
104cbd5, "cgroups: use task_lock() for access tsk->cgroups safe in
cgroup_clone()"), thus resulted in lock inconsistency.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li Zefan 2009-01-29 14:25:21 -08:00 committed by Linus Torvalds
parent 945048ca36
commit 1404f06565
1 changed files with 7 additions and 6 deletions
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13
kernel/cgroup.c
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@ -2993,20 +2993,21 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
mutex_unlock(&cgroup_mutex);
return 0;
}
task_lock(tsk);
cg = tsk->cgroups;
parent = task_cgroup(tsk, subsys->subsys_id);
/* Pin the hierarchy */
if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
if (!atomic_inc_not_zero(&root->sb->s_active)) {
/* We race with the final deactivate_super() */
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Keep the cgroup alive */
task_lock(tsk);
parent = task_cgroup(tsk, subsys->subsys_id);
cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
mutex_unlock(&cgroup_mutex);
/* Now do the VFS work to create a cgroup */
@ -3045,7 +3046,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
mutex_unlock(&inode->i_mutex);
put_css_set(cg);
deactivate_super(parent->root->sb);
deactivate_super(root->sb);
/* The cgroup is still accessible in the VFS, but
* we're not going to try to rmdir() it at this
* point. */
@ -3071,7 +3072,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
deactivate_super(parent->root->sb);
deactivate_super(root->sb);
return ret;
}